Does ghost exist? Ever wonder what a spirit is?

In my understanding, there is good and bad sprits every where we go.
Just recently a friend of mind told me that she is being disturbed by a spirit who consistently waking her up every night in her sleeps. As her friend I understand that she wouldn’t joke about things like this. And in the past few days, staying with her I was also disturbed by the spirits and I could not understand where they come from and what they want and how should I get rid of them. I meditated and also chants but nothing seem to work. So I did a research on these spirits/ghosts. I studies really hard and also consulted some wiser teacher who have been practicing meditation.

Then today a wise man told me: Our mind is really powerful. It can connect us to the spirit’s world when we allowed it. When we think of it a lot, there is when we are giving out the signal to them to enter our mind, but if we train our mind not to think of the spirits then we are actually lowering the connection signal. And these spirits can not get through to our mind, so they will slowly disappear. Through meditation we can calm our mind and also free our self from habitual states of greed, hatred and delusion.